There are traction control devices (refer to Japanese Patent Laid-Open Publication No. 05-86920 for an example) in which the acceleration slip of wheels is detected based upon the detection output from respective wheel speed sensors installed in an ABS (anti-skid brake system). Thus, the acceleration slip is suppressed by the traction control devices.
In such traction control devices, for example, a brake ECU for controlling an ABS actuator receives detection signals from each wheel speed sensor, as well as detection signals sent from a vehicle speed sensor via a power train module (equivalent to an engine ECU and hereinafter referred to as “PCM”). The brake ECU detects acceleration slip based upon the wheel speed and vehicle speed. If acceleration slip is detected, a signal indicating the acceleration slip is sent to the PCM and the brake ECU. Accordingly, the engine control amount is adjusted to lower engine output, and a motor and electromagnetic valves mounted in the ABS actuator are driven to generate a braking force in the wheels. Hence, the driving force generated in the wheels is reduced, suppressing acceleration slip.
Racing the engine when the vehicle is stopped transmits vibrations caused by rotation of the engine or the like to rotors installed in each wheel, via a drive shaft or the like. Accordingly, noise (a so-called racing noise) caused by such vibrations is included in the detection signal of the wheel speed sensor, which obtains a wheel speed detection signal based upon the rotation of the rotor. Therefore, the brake ECU obtains an erroneous detection result indicating that the wheel is rotating, despite the stopped state of the vehicle, from the detection signal of the wheel speed sensor affected by noise. A problem arises when the brake ECU executes traction control based upon this erroneous detection.
In such cases where the traction control is unnecessarily executed, for example, when the engine output is lowered through an engine control, the engine does not race, despite the attempt to make it do so. Furthermore, the driving sound of the motor and electromagnetic valves mounted in the ABS actuator when driven is audible even though there is no need for traction control.